Synthesis and study the mesomorphic behaviour of some new 1,3,4-thiadiazoline derivatives

Investigation of mesomorphic properties of new 1,3,4-thiadiazolines (which are synthesised via many steps in Scheme 1) was carried out in this study. These compounds are designed to have a heterocyclic unit, a carboxylate linkage group and a polar ether chain at the end of the molecule adjacent to the benzene ring, which enhance the dipolar interactions forces (varied from one to eight carbons) to investigate the association properties of their phases. The structure of the target compounds and the intermediates were confirmed by H-1 NMR, C-13 NMR, mass and FTIR spectral techniques. Polarised microscopic studies revealed that all the compounds in the series exhibited enantiotropic liquid crystalline properties. This was further confirmed using differential scanning calorimetric experiments. The synthesised compounds type [V](n) in this study displayed different liquid crystalline mesophases and the homologous [V] having an alkoxy terminal group (n = 1-3) exhibited nematic phase, whilst the last derivatives of the series (4-8), displayed smectic A phase. [GRAPHICS] .